已知tanx=2,则3sin2x+2cos2x/cos2x-3sin2x的值为 _ .
问题描述:
已知tanx=2,则
的值为 ___ .3sin2x+2cos2x cos2x-3sin2x
答
∵tanx=2,则3sin2x+2cos2xcos2x-3sin2x=6sinxcosx+2(cos2x-sin2x)cos2x-sin2x-6sinxcosx=6sinxcosxsin2x+cos2x+2×cos2x-sin2xcos2x+sin2xcos2x-sin2x-6sinxcosxsin2x+cos2x=6tanx1+tan2x+2×1-tan2x1+tan2x1-tan2x...